Many different designs of marker pencils for producing colored lines and markings and the like are known. In regard to the configuration of their writing member which comprises a solid material, a distinction is to be made between lead pencils and chalks. Thus for example while colored pencils have a thin lead which is enclosed and supported by a casing, colored chalks do not require such a casing by virtue of their substantially greater thickness, in comparison with colored pencils, the thickness of chalks being for example about between 7 and 10 mm.
The lead and chalk materials of marker pencils and chalks, besides a coloring agent or dye carrier, also contain a binding agent and a lubricating and adhesive substance, while various filler substances may also be added. The binding agent, for example cellulose derivatives and plastic materials, afford the leads and chalks adequate strength, that is to say a degree of strength which withstands the pressure applied thereto in situations of use. The lubricating and adhesive substances ensure that the pencil can glide smoothly over the surface of the item or material on which a marking is to be produced, for example the surface of a sheet of paper, while producing a marking which adheres firmly to that surface. For that purpose the leads may be impregnated with a grease or fatty substance. In the case of the leads or pencil leads which are referred to as wax pencils or wax pencil leads and also in the case of chalks, the fatty substances such as paraffin, animal and vegetable fats, Japan wax, stearines or synthetic waxes are incorporated into the pencil lead material. Besides the fatty substances, the pencils or pencil leads may also include water-soluble and/or water-insoluble metal soaps in order to improve the slidability of the pencil. If the metal soaps are water-soluble, they also act as an emulsifier for the fatty substances, but they do not represent a structure-forming constituent for the lead or the pencil.
The emulsifier effect of the metal soaps is however restricted to the manufacturing process as the water which is temporarily present in the pencil or lead material, by virtue of the deformability thereof, is removed after the shaping operation, by drying at elevated temperature.
It is possible to modify the physical properties and in particular the hardness of the pencil or the pencil lead by virtue of a suitable selection of the binding agent and the fatty substances used. The coloring effect produced substantially depends on the chemical composition of the pencil material, in which respect an important consideration is that the marking which is left behind on the paper is intensively colored.
Colored leads and colored chalks are basically produced by a procedure in which solvents (water or mixtures of water with water-soluble organic solvents) are added to dry pencil material in order to impart thereto a consistency which is required for shaping by means of extrusion or screw-pressing, and the extruded material is then cut to the desired length and then dried. Lead materials with a higher content of fats and waxes can be formed into elongate portions by known extrusion processes, without the addition of solvents, and then cut to the desired length. The extrusion operation may possibly be carried out at elevated temperature.
Although the writing properties of the above-described marking pencils may be modified to a certain extent by varying the proportions and the chemical composition of the above-mentioned base constituents and also by the addition of auxiliary constituents, for many purposes the marking effect of even those pencils which are adjusted to have a low level of hardness is still found not to be sufficiently soft. That would also apply for example in the situation where a marker pencil of the above-described kind incorporated a fluorescent dye carrier such as for example a daylight fluorescent dye with which written text on an article such as a sheet of paper is to be particularly emphasised by rubbing the pencil over same. The color or fluorescent effect would also suffer from the point that, when using such a pencil, too little pencil material and thus also an inadequate amount of dye carrier is applied to the paper.
For that reason, hitherto marker pens have been used for the last-mentioned purpose, which comprise a housing which accommodates a dyestuff solution (ink) and a capillary storage member for the solution, and a capillary member for conveying the dyestuff solution from the interior of the housing outwardly and for applying it to the paper. In that situation the liquid discharge of the dyestuff is found to be more pleasant and agreeable in comparison with the above-described colored lead pens and colored chalks, in particular when the marking to be produced is to be particularly wide and the capillary writing tip is made from a soft material.
However, in order for the tip of the marker to enjoy sufficient strength throughout the entire period of use of the marker, particularly when such tips are used in a refillable marker pencil, the tips have to be made from a suitable, preferably sintered plastic material. That however means that although such writing tips are resilient, they do however present a certain degree of basic hardness which excludes permanent deformation of the tip.
If a marker of that kind is used to cover a large wide area for example on a sheet of paper, as is frequently required by artists and in graphic design, then the use of such markers frequently results in the coloring effect being stripey and streaky and generally uneven, which is undesirable. That then does not provide a uniform even marking.
When a dye pigment which is dispersed in the fluid is used, problems can arise due to blockage of the capillaries of the applicator member. Finally, the plastic components which are used in liquid markers, such as the housing, storage member and applicator member, which generally involve different kinds of plastic materials, give rise to a relatively high level of expenditure on material and thus a relatively high level of overall costs, while in addition causing major problems in regard to disposal and in particular in regard to recycling the different kinds of plastic materials. Conventional liquid markers can hitherto only be subjected to energy recycling by way of a refuse incinerator installation.